Refinement of the isomorphic substitutions in goethite and hematite by the Rietveld method, and relevance to bauxite characterisation and processing

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• 作者：Reiner Neumann ; Angela Nair Avelar ; Geraldo Magela da Costa
• 关键词：Bauxite ; X-ray diffraction ; Rietveld method ; Mineral phase quantification ; Isomorphous substitution ; Mixed crystals
• 刊名：Minerals Engineering
• 出版年：January, 2014
• 年：2014
• 卷：55
• 期：Complete
• 页码：80-86
• 全文大小：1090 K

文摘

Although bauxites usually have a quite simple mineralogy - gibbsite (+boehmite), quartz, kaolinite, hematite, goethite, anatase (+rutile) and minor or less common phases, fine particle size, low crystallinity and variable compositions of the iron minerals might render phase quantification difficult, as well as impairing bauxite processing. A reliable and complete characterisation is therefore necessary in order to predict processing performance and ensure compliance to plant specifications.

X-ray diffraction is the most important single tool for bauxite characterisation, and the constrained refinement of the Al-for-Fe substitution in goethite during one-step phase quantification by fundamental parameters Rietveld method has been successfully used. The same method was developed to analyse the coupled Al-for-Fe and OH^{鈭?/sup>-for-O2鈭?/sup> substitutions in hematite. The method was tested against M枚ssbauer spectroscopy iron distribution on bauxite samples with a large compositional range, and on bauxite Certified Reference Materials from the main Brazilian mines, with improved results and widened range of conclusions that can be drawn related to bauxite processing.}